'Once Upon a Time': Emma protests Regina going undercover

When Regina (Lana Parrilla) goes undercover to infiltrate the Queens of Darkness on Sunday’s episode of Once Upon a Time, a surprising ally will try to convince her against it: Emma (Jennifer Morrison).

Fortunately, by that time, Regina has already learned that Maleficent (Kristen Bauer van Straten) & Co. are after the Author, and are planning to use Regina to steal a piece of information that could help them locate him. How will Emma react? Find out in our exclusive sneak peek.